Standardize construction of pathnames with extensions when multiple periods are involved

constructPathname.swift

import Foundation
import PlaygroundSupport

func constructPathname(pathname: URL, name: String, ext: String) -> URL {
  let n = name.hasSuffix(".") ? String(name.dropLast()) : name
  let x = ext.hasPrefix(".") ? String(ext.dropFirst()) : ext
  return pathname.appendingPathComponent("\(n).\(x)")
}

print(constructPathname(pathname: playgroundSharedDataDirectory, name: "Tea, Inc.", ext: ".json"))
print(constructPathname(pathname: playgroundSharedDataDirectory, name: "Tea, Inc.", ext: "json"))
print(constructPathname(pathname: playgroundSharedDataDirectory, name: "Tea, Inc", ext: "json"))
print(constructPathname(pathname: playgroundSharedDataDirectory, name: "Tea, Inc", ext: ".json"))